There are a lot of books on the 69 and 86 teams – most of them are ok. But for me one of the best Mets books ever published was about the 1962 team that lost 120 games.
In Can’t Anybody Here Play This Game?: The Improbable Saga of the New York Met’s First Year, Jimmy Breslin (one of the great newspaper writers of the 20th century) captures the ineptitude and “lovable loser” mythos of that first year club. Republished recently it’s a must have for any Mets fan (makes a great gift).